textproduct: Quad Cities

KEY MESSAGES

- Slight/Enhanced Risk (level 2/3 of 5) for severe storms early this morning around sunrise, lasting through mid morning.The primary threat with these storms will be large to very large hail.

- Late this morning and through the afternoon, much of the area will have a threat for more severe storms, with the whole area under a severe threat ranging from a Slight Risk (level 2 of 5) in our northwest to a Moderate Risk (level 4 of 5) in our extreme southeast/east.

- High moisture content over the area will allow for heavy rainfall with any storms through today. Flash flooding will be possible in areas that see repeating rounds of storms, especially in areas that recently saw heavy rainfall. Flood Watch remains in effect for areas in West-Central Illinois.

- Quiet weather will be seen through the second half of the work week, with the pattern becoming active again this weekend and beyond.

SHORT TERM /THROUGH TONIGHT/

Issued at 215 AM CDT Wed Jun 17 2026

Severe weather is expected today as a seasonably strong system moves through the region. This will bring two rounds of storms to eastern Iowa, northwest Illinois, and northeast Missouri: a first round in the morning hours (4-9 AM) and second round in the afternoon hours (12-7 PM). Morning storms are anticipated to have a primary threat of large hail and low damaging wind potential, while afternoon storms will be capable of all hazards, including tornadoes. In addition, heavy rain will lead to localized flash flooding, especially in areas that see repeated rounds of storms.

A strong shortwave will move from the Northern Plains into the Upper Midwest this morning. Pressure heights are near or at the NAEFS climatological minimum for mid-June, while winds aloft are near or at their maximum. This can be seen in a strong (50-60 kts) zonal jet at 500 mb sampled upstream with today's 00Z soundings. As this system translates into the Upper Midwest early this morning, southerly to southwesterly flow across the central Plains will provide warm air advection and moisture, which will amplify with the LLJ towards sunrise. As a result, dewpoints are forecast to rise into the mid to upper 60s within a few hours after sunrise, creating a sharp gradient between the northern and southern halves of the CWA. Lift along this WAA wing will provide the focus for morning convection, with showers and storms across the area.

For the morning, the greatest risk for severe storms is along and south of Interstate 80, though there is some uncertainty given a strong cap over the region. If storms are able to develop, shear magnitude and direction suggests a mixed storm mode with multicell and supercells storms. A favorable severe environment of high lapse rates (7.5-8.5 degC/km) and up to 2000 J/kg of MUCAPE will support a primary risk of large hail. In addition to the risk of large hail, heavy rain will be possible with these these storms. This should be a soaking rain this morning and flash flooding threat should be limited, save for areas that have a long residence time with storms. This would primarily occur with cells that move over the same areas, as storms in this first round will be moving quickly towards the east at 40-50 kts.

By mid- to late morning, these storms will move east into central Illinois, giving the airmass time to recover. At this point, strong southwesterly flow will continue to feed in moisture and instability, providing the energy necessary for the second round of storms. The greatest area of uncertainty is in how much recovery time will be possible, as morning storms and showers could persist longer than anticipated. If the atmosphere is able to recover following morning storms, an environment favoring supercells will develop, leading to the potential for all hazard severe thunderstorms.

Around 12 PM, forcing along the cold front will plow into a region of 2000 (north) to 4000 (south) J/kg of CAPE, providing the forcing necessary for convective initiation. These storms will be fast moving, with a storm motion of 50 kts to the east. Large hail and damaging winds are possible with all storms. Tornado threat will be more limited, with the best low level shear supporting the highest tornado threat in west-central Illinois. These storms will exit into central Illinois around 6-7 PM.

Once these storms move off to our east, CAA advection behind the front will support westerly to northwesterly winds up to 20-25 mph, leading to a breezy night.

LONG TERM /THURSDAY THROUGH TUESDAY/

Issued at 215 AM CDT Wed Jun 17 2026

Several pleasant, mainly dry days will follow our big system today. This will lead to temperatures below normal for highs and lows Thursday and Friday. Dry air should keep any rain threat low, though some energy skirting by aloft could bring some sprinkles or even a tiny thunderstorm as early as Friday night.

Warm begins to spread northward again towards Saturday, as the flow aloft shifts towards a more active zonal flow regime. Models remain consistent in showing a warm front developing over the Midwest Saturday night, and having at least one significant wave of rain and thunderstorms/ potentially an MCS Sunday and Sunday night. There is latitude differences in the latest deterministic guidance, with the GFS shifting that axis a bit south, and the EC and GEM maintaining a more northerly frontal zone. Regardless, that will be the next period for us to focus on for both heavy rainfall and a thunderstorm risk.

AVIATION /06Z TAFS THROUGH 06Z THURSDAY/

Issued at 1210 AM CDT Wed Jun 17 2026

A fast moving storm system will bring a quick transition from VFR with light winds to thunderstorms with very strong winds aloft (LLWS) towards morning. Storms are expected to rapidly form in eastern Iowa between 09z and 12Z, then spread quickly southeast and east through the rest of the area. These storms will move quickly, produce lots of lightning, hail, and gusty winds, in addition to IFR conditions in the storms. This period of widespread storms will extend towards 18z, especially along and north of Interstate 80 Wednesday. More isolated coverage, but intense storms are possible in the afternoon, mainly at MLI and BRL, (south of I-80). These storms could also produce damaging winds, hail, and some tornadoes as well. Quick movement to the east should limit the duration of impact to aviation, with a breezy, but largely VFR evening expected behind the afternoon storm threat.

DVN WATCHES/WARNINGS/ADVISORIES

IA...None. IL...Flood Watch from 7 AM CDT this morning through this evening for ILZ009-016>018. MO...None.